After an estimated 15,000 protesters flooded the central plaza of Guatemala City on Saturday in a grassroots anti-corruption demonstration, President Otto Perez Molina promised justice but said he would not be stepping down as protesters demanded.

The weekend protest was organized entirely on social media and seems to have caught top political leaders by surprise. Demonstrators also called for the resignation of Vice President Roxana Baldetti, after a United Nations anti-corruption body revealed a tax-fraud and customs scandal involving dozens of high-ranking officials.

“As president, I repeat my commitment to the free liberty of expression of all Guatemalans. I’ve received your message loud and clear,” Perez Molina said in a televised statement on Monday. “It doesn’t matter who you are, you must face the full weight of the law with due process.”